1. Field of the Invention
The present invention relates to a time sharing type multi-beam radar apparatus.
2. Description of the Related Art
Time sharing type multi-beam radar apparatuses using microwaves and millimeter waves have been mounted on vehicles to obtain an azimuth angle and distance of a near object.
A prior art time sharing type multi-beam radar apparatus is constructed by a plurality of transmitting/receiving antennas each connected to one transmitter, one receiver and one diplexer such as one circulator (see JP-A-6-242230, JP-A-7-5252 and JP-A-8-262133). In this case, each of the transmitting/receiving antennas has a transmitting antenna pattern and a receiving antenna pattern the same as the transmitting antenna pattern, so that a transmitting/receiving operation is carried out by a mixed antenna pattern of the transmitting antenna pattern and the receiving antenna pattern. Therefore, if the number of the transmitting/receiving antennas if four, the number of mixed antenna patterns is four.
In the above-described prior art time sharing type multi-beam radar apparatus, however, in order to enhance the detection accuracy, the number of transmitting/receiving antennas needs to be increased, which would increase the manufacturing cost. In addition, if the number of transmitting/receiving antennas is increased, the side lobe characteristics are deteriorated, which deteriorates the antenna gain. As a result, the detection accuracy cannot be enhanced.
It is an object of the present invention to provide a time sharing type multi-beam radar apparatus capable of enhancing the detection accuracy without increasing the manufacturing cost.
According to the present invention, in a time sharing type multi-beam radar apparatus, a plurality of transmitting antennas are arranged in a first row, and each of the transmitting antennas has a first antenna pattern. Also, a plurality of receiving antennas are arranged in a second row in parallel with the first row, and each of the receiving antennas has a second antenna pattern. The first and second antenna patterns adjacent to each other spatially and partly overlap each other.
Thus, if the number of transmitting antennas if four and the number of receiving antennas is four, which correspond to the case where the number of transmitting/receiving antennas is four, the number of mixed antenna patterns is seven, thus substantially decreasing the number of antennas. Also, since the side lobe characteristics are improved, the antenna gain can be enhanced, which would enhance the detection accuracy.